1. Field
This invention relates generally to mist removal separator vanes and more particularly to a fixture for in-situ cleaning of mist removal separator vanes to remove scale build-up.
2. Description of Related Art
In general, mist removal separator vanes are installed in components wherein moisture is removed from saturated steam. The mist removal separator vanes are capable to remove liquid droplets among the steam vapor. For example, the mist removal separator vanes aggregate the mist in the pockets of the vanes and let them flow down the pockets to separate the liquid from the steam vapor. It is known to use mist removal separator vanes in a variety of components and applications. Mist removal separator vane assemblies are used in the nuclear industry as well as in non-nuclear applications. In non-nuclear facilities, mist removal separator vane assemblies are installed in moisture separators and similar components. In nuclear plants, mist removal separator vane assemblies are also installed in steam generators.
In general, the installation and operation of mist removal separator vane assemblies in steam generators results in scale build-up on the vane assemblies. The rate of scale build-up depends on the rate of ingress of particulate material such as magnetite into the steam generators.
A nuclear reactor, such as a pressurized water reactor or a heavy water reactor, contains steam generators in which a separate stream of water circulates in a heat transfer relationship with the primary fluid. The steam generator typically consists of a vertically-oriented shell and a plurality of U-shaped tubes disposed in the shell so as to form a tube bundle. The primary fluid is heated by circulation through the reactor and enters the steam generator through a primary fluid inlet, flows through the U-tube bundle and out a primary fluid outlet to the remainder of the reactor coolant system. At the same time, feedwater is introduced into the steam generator secondary side, i.e., the side of the steam generator interfacing with the outside of the tube bundle. Heat is transferred from the primary fluid in the tubes to water surrounding the tubes causing a portion of the water surrounding the tubes to be converted to steam. The mixture of steam and water then rises and is conducted through a number of moisture separators that separate entrained water from the steam, and the steam vapor then exits the steam generator and is typically circulated through a turbine to generate electricity in a manner well known in the art. Mist removal separator vane assemblies can be located in the steam generators (e.g., secondary side) and/or the moisture separators.
The ingress of particulate material such as magnetite contained in the feedwater which circulates through the steam generator can cause scale build-up in the mist removal separator vane assemblies located in the steam generator. As a result, the effectiveness of the mist removal separator vanes decreases over time and the amount of moisture carryover in the steam increases. Increase in moisture carryover is undesirable for efficient plant operation. Thus, it is beneficial to clean the vane assemblies to remove the scale build-up and restore their effectiveness.
The mist removal separator vane assemblies can include a wide variety of designs and configurations. Generally, the mist removal separator vanes which are installed inside steam generators of nuclear reactors have a zigzag geometry and several embedded pockets. This particular design, while effective for removing moisture from the steam flow, is difficult to clean without dismantling the vane assembly. Further, in certain steam generator designs, there is a perforated plate welded to the inlet face of the vane assembly which further obstructs access to the vanes for cleaning. Removal of the vanes from the steam generator can require significant time and labor which can thereby result in additional costs.
It is an object of the embodiments described herein to provide a cleaning fixture for in-situ cleaning of the mist removal separator vane assemblies positioned in various components, e.g., nuclear and non-nuclear applications, such that the dismantling of the mist removal separator vane assemblies is not necessary to effectively clean the vanes.